How do I get the size of a directory in C?

Question

Is there a POSIX function that will give me the size of a directory (including all sub-folders), roughly equivalent to "du -s somepath"?

Answer 1

There is no ready-made function, so you will have to make your own. You may look at the source code of the GNU implemenation of du as an example (see http://www.gnu.org/prep/ftp.html for a list of places to download from). It is in the coreutils package.

The crucial Posix calls are probably opendir, readdir, closedir, and stat.

Answer 2

$ man nftw

NAME

ftw, nftw - file tree walk

DESCRIPTION

ftw() walks through the directory tree that is located under the directory dirpath, and calls fn() once for each entry in the tree. By default, directories are handled before the files and subdirectories they contain (pre-order traversal).

CONFORMING TO

POSIX.1-2001, SVr4, SUSv1.

Simple example

#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>

static unsigned int total = 0;

int sum(const char *fpath, const struct stat *sb, int typeflag) {
    total += sb->st_size;
    return 0;
}

int main(int argc, char **argv) {
    if (!argv[1] || access(argv[1], R_OK)) {
        return 1;
    }
    if (ftw(argv[1], &sum, 1)) {
        perror("ftw");
        return 2;
    }
    printf("%s: %u\n", argv[1], total);
    return 0;
}